Centimeters and millimeters are commonly used measurement units to calculate distance in the metric system. The prefix "centi" means "hundred", meaning that there is 100 centimeters in 1 meter. "Mili" means "thousand", so there are 1,000 millimeters in 1 meter. Because they are so similar, conversion from one to the other is very common. There are 10 millimeters in 1 centimeter, so one way to do this conversion is to multiply the desired number by 10. The metric system is designed to be easily converted with a simple decimal point change, without having to do complex calculations. With practice, you can make these changes faster and faster.

## Steps

### Method 1 of 3: Making Conversion Calculations

#### Step 1. Find the number in centimeters you want to convert

For example, if you are trying to solve a problem, read the statement to find the different measurement units used. See if the question gives the length in centimeters (cm) and asks for the result in millimeters (mm). When taking a measurement, take it in centimeters. Measuring in millimeters is difficult as it is a very small unit, but it can be easily obtained after a conversion from centimeters.

### An example question might be, “The width of a table is 58, 75 centimeters. What is the width measurement in millimeters?”

#### Step 2. Multiply the centimeter value by 10 to find the answer in millimeters

Remember that 1 cm = 10 mm, so you can convert any value to centimeters with just this multiplication.

- Following the example: 58.75 cm x 10 = 587, 5 mm.
- The millimeter is a smaller unit than the centimeter, even though they both have the word "meter" in them. Multiplication is always used to transform a larger unit of measure into a smaller one.

#### Step 3. Divide the millimeter value by 10 to get the centimeter value

There are 10 mm in 1 cm, so converting from millimeter to centimeter is also very simple. Start the calculation using the mm measurement, and if you got this value from a cm measurement, compare the two results to see if you did the right math.

- A possible statement: “The height of a door is 1780, 9 millimeters. Find the measurement in centimeters.” The answer is 178.09 cm, since 1780, 9 mm ÷ 10 = 178.09 cm.
- Keep in mind that millimeters is a unit smaller than centimeters, and this conversion requires a division.

### Method 2 of 3: Moving the Comma

#### Step 1. Find the comma in the number you want to convert

When solving an issue, first identify the measurement in centimeters. When taking a measurement, take it in this unit. Look for the comma and, if the number has no decimal places, suppose it is at the end of the number.

- For example, assuming that the problem asks for the length of a TV with 32.4 cm in millimeters, the position of the comma is important to make the conversion quickly and without calculations.
- For whole numbers like 32 cm, the comma is at the end, as in 32, 0 cm.

#### Step 2. Move the decimal point 1 decimal place to the right to get the value in mm

Moving a decimal in this way is the same as multiplying the number by 10. The way the metric system works, you don't need to use a calculator. Since 1 cm = 10 mm, this is shown by changing the comma.

- 32, 4 cm becomes 324.0 mm when you walk the comma to the right one square. Check the result by making 32.4 cm x 10 = 324, 0 mm.
- For whole numbers like 32 cm, write the decimal place represented by a 0 at the end of the number, then change the position. As in, 32.0 cm x 10 = 320.0 mm.

#### Step 3. Move the decimal point one decimal place to the left to get the centimeter value again

If you need to return the value to centimeters or want to check the result, just move the comma back. There are 10 mm in 1 cm, which is why it moves to the left. You can confirm this phenomenon with a simple math account.

- In a statement: “The height of the chair measures 958, 3 millimeters. Find the measurement in centimeters.” Walking with the comma gets the result of 95.83 cm.
- To check the bill, divide the value by 10, so 958, 3 mm ÷ 10 = 95.83 cm.

### Method 3 of 3: Practicing Conversions

#### Step 1. Try converting 184 cm to mm

This problem asks you to exercise the conversion in two different ways: Multiplying the value by 10, or shifting the decimal point one decimal place to the right. Both methods should achieve the same result.

- Mathematically: 184 cm x 10 = 1840 mm.
- Using the comma shift, write 184.0 cm. Walk a house with her to get 1840, 0 mm.

#### Step 2. Convert 90, 5mm to centimeters

Note that this question starts with a measurement in millimeters. Knowing the conversion from one to the other, you can easily do the opposite operation to get the desired result. One way is to divide the value by 10, and another is to move the comma one place to the left.

- Mathematically, 90, 5 mm ÷ 10 = 9,05 cm.
- With the comma technique, starting from 90, 5 mm, move one decimal place to the left to obtain 9,05 cm.

#### Step 3. Change 72, 6cm to millimeters

This conversion can be done with either method. Remembering that there are 10 millimeters in 1 centimeter, multiply the value by 10 or go one space to the right with the comma.

- Using a math bead, 72, 6 cm x 10 = 726 mm.
- Otherwise, 72.6 cm becomes 726 mm.

#### Step 4. Convert 315mm to centimeters

Note the initial unit in mm. This is important to get the correct value so that the value is divided by 10, not multiplied. With the comma technique, move one decimal place to the left.

- For example, 315 mm ÷ 10 = 31.5 cm.
- Or pass 315.0 mm to 31.5 cm.

## Tips

- The same conversion technique can be used in other units of the metric system such as from meters to kilometers.
- One meter is equal to 100 centimeters and 1000 millimeters. Since all words contain the suffix "meter", they can become confusing.
- If you need help performing a conversion, use an online calculator to get the desired value.